The invention relates to a control system for coupling two final control elements as regards the actuated position and the actuating force.
EP 0 591 890 A1 has disclosed a control system of the type stated at the outset which is designed as a synchronisation control system and synchronises or couples a pilot""s joystick and a copilot""s joystick as regards the actuated position and the actuating force. For this purpose, the known synchronisation control system has two force-control loops of identical construction. In each of these force-control loops, the joystick serving as a final control element actuates an actual-force transmitter for producing an actual-force signal correlating with forces prevailing at the joystick and an actual-position transmitter for producing an actual-position signal correlating with the actuated position selected at the joystick. Each of the force-control loops furthermore has a desired-force generator, which generates a desired-force signal from the actual-position signal as a function of a specified relationship between actuated positions and actuating forces. Moreover, each force-control loop has a force controller which, as a function of the force signals present at an input of the force controller, actuates a force actuator in such a way that the specified relationship between the actuated positions and the actuating forces is established at the joystick. The two force-control loops are coupled to one another by way of their actual-force signals, that is to say the actual-force signals of one (first) force-control loop are additionally fed to the input of the force controller of the other (second) force-control loop, and the actual-force signals of the second force-control loop are additionally fed to the input of the force controller of the first force-control loop. With the aid of this synchronisation control system, the one joystick can rapidly and accurately adopt the position, selected at the other joystick. Moreover, the forces or moments applied at one joystick can be felt very precisely and directly at the other joystick. The synchronisation of the two joysticks is equivalent to play-free mechanical coupling in terms of its directness, rapidity and accuracy.
The present invention deals with the problem of specifying an embodiment for a control system of the type stated at the outset that is versatile in use.
This problem is solved by means of a control system according to the invention herein.
The invention is based on the general idea of coupling the two force-control loops to one another by way of a proportionality factor. By means of this measure, it is possible to achieve a force transmission ratio between the two final control elements that makes the control system versatile in terms of its uses.
For example, the control system configured in accordance with the invention can be used on a gripping arm that has a manually actuated handle and gripping tongs for gripping heavy objects. Here, the handle forms the first final control element and is assigned to one force-control loop, while the gripping tongs form the second final control element, which is assigned to the other force-control loop. By means of the handle, a user can actuate the gripping tongs in order to grip an object. At the same time, the control system according to the invention can be set in such a way that a relatively small force introduced manually into the handle produces a relatively large gripping force at the gripping tongs.
It is particularly advantageous if the control system according to the invention is used to form a steer-by-wire steering system in a motor vehicle. The final control element of one force-control loop is here formed by the steering handle, e.g. steering wheel, of the vehicle while the final control element of the second force-control loop is formed by the steered vehicle wheels while the final control element of the second force-control loop is formed by the steered vehicle wheels. The directness, rapidity and accuracy of coupling between the two final control elements, or steering handle and steered vehicle wheels, as described above gives the driver a particularly good feeling for the forces prevailing at the steered vehicle wheels and thus for the road over which the vehicle is travelling. In this arrangement, the transmission ratio produced by the proportionality factor between the steering forces acting at the two final control elements (steering handle and steered vehicle wheels) brings about servo assistance.
In a particularly advantageous embodiment of the control system according to the invention, the relationship between the actuated positions and actuating forces of the associated final control element which is specified in the desired-force generator of one force-control loop can differ from the relationship specified in the desired-force generator of the other force control loop for the actuated positions and actuating forces of the corresponding other final control element. This measure has the effect of a transmission ratio between the actuating movements of one final control element, e.g. the steering handle, and the adjusting movements of the other final control element, e.g. the steered vehicle wheels. The adaptability of the control system according to the invention to different applications is thereby considerably increased. For example, this means that the control system can be adapted particularly well to the conditions prevailing in a vehicle steering system so that the control system can be used in a steer-by-wire steering system. In general, the steering angle established at the steering handle in a vehicle is considerably larger than the associated steering angle assumed by the steered vehicle wheels, with the result that a transmission ratio is required between the adjusting movements of these final control elements. Instead of a complicated mechanism, this transmission ratio is here achieved by means of appropriate adaptation, e.g. by means of a correction factor, of the relationship between the actuated position and the actuating force of at least one of the final control elements.
In an advantageous embodiment, the proportionality factor can be varied as a function of parameters, thereby allowing the force transmission ratio between the force-control loops to be made dependent on parameters. In a preferred embodiment, for example, this means that the vehicle steering can operate with little servo assistance, i.e. in a relatively stiff manner, at relatively high vehicle speeds and with a large amount of servo assistance, i.e. relatively easily, at relatively low vehicle speeds, e.g. for manoeuvring.
According to a development of the control system according to the invention, the relationship between the actuated positions and the actuating forces of the final control element in one force-control loop and/or in the other force-control loop can be varied as a function of parameters. In these embodiments, mass/spring-damping characteristics can be incorporated into the steering system when the control system is used in a steer-by-wire steering system of a vehicle, for example, these characteristics enabling self-centring of the steered vehicle wheels, for example. It is likewise possible, by means of these embodiments, preferably as a function of the vehicle speed, to alter the transmission ratio of the movements of the final control elements, i.e. the association between steering angles at the steering wheel and steering angles at the vehicle wheels.
What has been said about xe2x80x9cforcesxe2x80x9d in this description applies also in a corresponding manner to xe2x80x9cmomentsxe2x80x9d and, in particular, it is likewise possible for moments to be picked off or introduced at the final control elements instead of forces.
Further important features and advantages of the control system according to the invention will become apparent from the subclaims, the drawing and the associated description of the figures with reference to the drawing.
It is self-evident that the abovementioned features and those yet to be mentioned can be employed not only in the respectively indicated combination but also in other combinations or alone without departing from the scope of the present invention.
A preferred exemplary embodiment of the invention is illustrated in the drawing and is explained in greater detail in the following description.